Agriculture is an important industry with considerable research and investment into improving processes and efficiencies. One important area of research is into ways of controlling pests which may cause significant damage to crops. Crops can be attacked by a wide range of pests and various strategies have been employed to control, kill or deter them.
One such approach involves synthetic insecticides which have been used over the last 50 years to control insect pests. Heavy use of these insecticides can exert a strong selection pressure on individual insects with mutations and this has led to increasing insect resistance to the insecticides.
An alternative approach was developed by incorporating the use of insecticidal proteins, for example Bacillus thuringiensis (Bt), in both sprays and genetically engineered crops e.g., Bt cotton. Transgenic crops, especially cotton, are now grown in many countries to control insect pests and their introduction has reduced synthetic insecticide use against some pests to a high degree. For example, in the Australian cotton industry, transgenic cotton crops (Bollgard II®) are planted in 95% of the area to manage Helicoverpa spp. By contrast, only 5% is planted to conventional cotton crops.
The introduction and adoption of transgenic cotton crops has reduced the importance of Helicoverpa spp. as major cotton pests in Australia. Furthermore, the sustained control of Helicoverpa spp. by various transgenic cotton crops has also significantly reduced the need to use synthetic insecticide against these pests. However, since the synthetic insecticides previously used to control Helicoverpa spp. also inadvertently suppressed sucking pest populations, the reduced reliance on insecticides for control of Helicoverpa spp. i.e., as a result of widespread adoption of transgenic cotton crops, has increased the threat posed by sucking pests such as, for example, green mirids (Creontiades dilutus), aphids (Aphis gossypii), green vegetable bug (Nezara viridula) and silverleaf whitefly (Bemisia tabaci). As such, the transition from conventional to transgenic cotton has led to an increase in the presence of pests that are unaffected by the toxin in the transgenic plants, which in turn has led to increased use of synthetic insecticides to control them.
Currently, cotton growers still face the problem of Helicoverpa spp. resistance, and the emergence of silverleaf whiteflies, green mirids, green vegetable bugs, aphids, two-spotted mites, and mealybugs etc. as more prevalent pests has resulted in yield loss. Soil pests such as wireworms are still an issue in most growing areas. Pupae busting is also a major issue for growers in order to comply with the Bollgard II® resistance management plan. The use of cheaper broad spectrum insecticides such as pyrethroids has increased partly due to the endosulfan ban and the high cost of cotton production. This increase in use of broad spectrum insecticides can cause disruption of beneficial insect populations and be counter-productive to integrated pest management (IPM) efforts, offsetting the benefits of IPM typically enabled by transgenic cotton lines. Thus, there is a continued need to develop new approaches as part of an IPM strategy to control agricultural pests, such as those affecting cotton crops.